1. Field of the Invention
This invention relates to a system for rapid tenderization of meat, especially poultry breast meat. This system prevents muscle fibers from contracting and toughening during the process of rigor mortis. The invention also relates to apparatus and methods for rapid tenderization of meat.
2. Description of the Related Art
The poultry industry in the United States currently processes about 29 billion pounds of broilers per year, with a wholesale value of more than $15 billion. Due to consumer preference and use in fast food sandwiches, the pectoralis major muscles of the poultry breast, specifically chicken, are worth about half the value of the entire carcass. Current industry practice for deboned poultry breast muscles require a prolonged chilling process or further aging if they are to be sold as whole breast fillets. To avoid consumer complaints about tough breast meat, purchasers require as much as 6-8 hours of on-the-bone aging before deboning. Current practice increases production costs because of the increased handling, increased refrigerated storage space, greater overall space requirement, interruption of product flow, needless chilling of bones that will eventually be discarded and difficulties of labor scheduling caused by the time difference between slaughter and deboning.
Meat research in the 1960's revealed that muscles removed from beef carcasses before or during rigor mortis produced an irreversibly tougher, cooked meat. The toughness was caused by contractions of the muscles freed from the skeleton, which normally limits the extent to which muscles can contract (R. L. Locker, Food Research, Volume 25, 304 1960; H. K. Herring et al., Journal of Science of Food and Agriculture, Volume 16, 379 1965). Thus, when the muscles remained on the beef carcass, the meat was less tough, and when the muscles were subjected to some tension during aging the meat was more tender (H. K. Herring et al., J. of Food Science, Volume 30, 1049, 1965). Using gravity to provide the tension force, different methods of hanging the carcass during aging determined which muscles became tender. However, the effect of muscle tension on intact poultry carcasses was not shown until the late 1980s, when poultry wings were stretched to increase breast muscle tension and produce a more tender meat (C. M. Papa and D. L. Fletcher, Poultry Science, Volume 67, 1988). The hanging method of the 1960's and the stretching method are equivalent, as they prevent contraction of the muscle.
Research into the effects of tension on excised muscles focused on muscle strips which were clamped on the ends and then pulled. Changes in contraction and tenderness were studied in beef, rabbit, turkey and chicken (H. K. Herring et al., J. of Food Science, Volume 32, 317, 1976; R. A. Jungk et al., J. Food Science, Volume 32, 158, 1967; R. A. Jungk and W.W. Marion, J. of Food Science, Volume 35, 143, 1970; A. A. Klose et al., J. of Food Science, Volume 35, 577 1970; D. F. Wood and J. F. Richards, J. of Food Science, Volume 39, 525, 1974; R. C. Whiting and J. F. Richards, J. of Food Science, Volume 40, 960, 1975). Methods for applying tension included sewing or tieing muscle ends (A. W. Khan, J. of Food Science, Volume 39, 393, 1974; A. A. Dunn et al., British Poultry Science, Volume 34, 677 1993).
Two studies of ovine muscle used clamping of muscle followed by freezing of the clamped samples. In both studies, prerigor muscles were clamped between two plates prior to excising the meat from the carcass. After excision, the clamped muscle was immediately frozen at -30.degree. C. with rapid air circulation on all sides. Muscle samples were removed from 15-336 hours post mortem. The carcass was stored at 1.degree. C. before the removal of the remaining post mortem samples. After 90 minutes, frozen samples were removed, unclamped, and stored for 6-10 days at 4.degree. C. or -5.degree. C. Meat was then cooked from the frozen state and tested for shearing strength. The most tender meat was obtained with a 7-10 day aging process after unclamping (M. Koohmaraie et al., J. of Animal Science, Volume 74, 2935 1996; T. L. Wheeler and M. Koohmaraie, J. of Animal Science, Volume 72, 1232 1994).
The present invention is different from related art tenderization apparatus and methods and overcomes problems encountered by current processing methods, namely, producing a poultry breast meat which is tender and does not require additional aging and added production costs.